1. Field
The present disclosure relates to tire treads comprising rubber compositions based on butyl rubber.
2. Description of Related Art
One of the requirements needed for a tire is to provide optimal grip on the road, especially on wet ground. One way of giving the tire increased grip on wet ground is to use a rubber composition in its tread, which composition has a broad hysteresis potential.
But at the same time, the tire tread must also minimize its contribution to the rolling resistance of the tire, that is to say have the lowest possible hysteresis. Thus, the rubber composition of the tread must satisfy two conflicting requirements, namely having a maximum hysteresis potential in order to satisfy the requirement of grip and having a hysteresis that is as low as possible in order to satisfy the requirement of rolling resistance.
Tire manufacturers have therefore proposed hysteretic materials, such as for example compositions based on copolymers of butadiene and styrene with a styrene weight content of at least 35%, rubber compositions comprising high contents of reinforcing fillers or plasticizers. But these solutions are generally obtained to the detriment of the rolling resistance.
It has also been proposed to introduce butyl rubber into the rubber compositions of the tire treads in order to improve their grip on wet ground. This is because butyl rubber is an elastomer whose dissipation potential is known and constitutes per se a good candidate for improving the grip, especially on wet ground, as U.S. Pat. No. 6,060,552 teaches. However, this patent also teaches that butyl rubber must be used at contents of at most 30 parts per hundred parts of elastomer (phr) in order to minimize its hysteretic contribution in the field of rolling resistance.
Patent EP 1 687 370 B1 discloses that the use, in a tire tread, of a rubber composition reinforced with a silica and comprising a certain content of butyl rubber and of glycerol trioleate makes it possible to improve the grip of the tire on wet ground. But this solution is not satisfactory with respect to the rolling resistance performance.
Satisfying both the requirement of grip, especially on wet ground, and of rolling resistance remains a constant concern of tire manufacturers.